Zip Files

What are Zip Files?

Zip files (.zip file extension) are compressed files, also known as 
archives and they can contain one or more files and generally are reduced 
in size due to various compression algorithms employed. One of the main 
uses of zip files is to make the exchange of files easier. Instead of 
having to send or download multiple files that might total several 
Megabytes in size, you send or download only one Zip file, which is 
considerably smaller because of the use of compression technology. 

Common methods of compression include eliminating empty spaces in the file, 
and eliminating repetitive characters or strings and replacing them with a 
key (that is much smaller...it is used to regenerate them when the file is 
de-compressed). Some files cannot be compressed, as they are already in 
compressed format. Files such as these are merely stored within the archive 
and no compression is used. An example of this would be an .MP3 sound file, 
or even including another .zip file within a ZIP archive. Note that there 
is still some benefit to doing this; simply having the desired files 
contained in a single archive file is convenient for Internet file 
transfers and also space is still saved by having everything in one file, 
as there will be less disk cluster overhang (wasted space due to only 
partial usage of disk allocation units). 

Another advantage of archiving files in .zip file format is that there will 
be less chance of corruption. If a .zip file gets corrupted, chances are it 
simply will not open (de-compress or extract). This is particularly 
significant for download purposes, as if you download a corrupted .zip file 
and it won't open you know to just download it again rather than installing 
a corrupted program or file. The ZIP file format contains a built in Cyclic 
Redundancy Check algorithm (CRC-32) for error checking both when the file 
is created, when extracted by utility on the other end, and can be done 
manually using the program's test function. Additionally, once created, a 
.zip file cannot be infected by viruses (provided it was clean when 
created!!). This means that a .zip file can sit there on a server or in a 
directory on your hard drive and the programs within cannot be infected. 

What does this have to do with me?

First and foremost, many of the files you will be downloading from the 
Internet will be in .zip format. If you haven't yet encountered these, you 
surely will and you need to be able to extract them. Also, you may want to 
learn how to create your own .zip files to facilitate sending email 
attachments to others, or simply to save disk space storing files for later 
use. Now, you need to download a ZIP utility. The next part of the tutorial 
covers the best utilities available. 

Which Zip Utility should I get?

The very first utility of it's kind was PKZip (and PKUnZip which was 
included) for DOS. The ZIP standard was created in 1989 by Phillip Katz, 
hence the name "PKZip". It was originally a DOS utility with usage similar 
to "PKUnZip filename.zip". That's no fun, so several Windows ZIP utilities 
were created. PKZip now comes in a Windows version in addition to the 
original DOS version and can be obtained at www.pkware.com. Note that this 
program is SHAREWARE. 

The most popular ZIP utility by far is Winzip. It is fast, easy to use and 
has a lot of useful features. It is my favorite and I wouldn't have a 
computer without it. 

Get Winzip - www.winzip.com 

The only thing wrong with Winzip is that it is SHAREWARE. The authors want 
money for the product. It is well worth the money, but if you want freeware, 
I recommend the following program, ZipGenius.  

Get ZipGenius - http://www.zipgenius.it

You can find more free Zip programs here: 
http://www.webattack.com/Freeware/downloader/fwzip.html

Depending on which program you choose, the menu options can vary slightly 
and may not exactly match the following instructions but they will be similar 
and you should be able to figure it out pretty quickly.

Install your program of choice, and let it assume the file association for 
.zip files. With Winzip (and most other Zip programs), this is done during 
setup. Simply choose Express Setup (recommended) and it will do this in 
addition to creating handy right-click Windows Explorer menu choices.  Now 
that you have a utility installed, we'll proceed with learning how to use it. 

Unzipping Files

You have just downloaded a program that came in the form of a .zip file and 
you have saved it to your download directory. Open Windows Explorer and 
browse to the directory where you have saved the .zip file. Double click 
the file to open it with WinZip (or your Zip utility of choice). I recommend 
that you just use Winzip in "classic mode" to have more control over what is 
going on. WinZip has a wizard, and if you chose that option during install, 
WinZip will open with the Wizard. You can change that though, just click 
Close when the Wizard pops up and then select the bullet to "start in 
classic mode". 

After double-clicking the file, the Zip program will display the contents of 
the .zip file. Any text files will be shown with a text file icon and you 
can double click them to automatically open them with notepad even before 
you unzip the file. This is especially handy for ReadMe files, as after 
reading it you may decide you don't even want to unzip the file and you can 
simply close the program and delete the file. At this point you can also 
invoke a virus scanner from within WinZip. Go to the Action menu in the 
program and choose Virus Scan. The first time you choose this, you will 
have to point it to where your Antivirus program's executable file is (e.g. 
C:\Program Files\Norton Antivirus\Navw32.exe). It will then scan the 
contents of the .zip file. 

To extract the contents of the file, choose Extract from the Action menu or 
simply click the Extract button on the toolbar. In the Extract To field, 
type the path to the directory you want to extract it to, or browse for it 
on the right by clicking the + signs to expand the folder trees on your 
drives. Choose either All Files or Selected Files (where only the 
highlighted file(s) will be extracted. When ready, click the Extract button 
in the dialogue. It will return to the main program screen and display the 
status (unless it's a really large file or you have a very slow computer it 
will be instantaneous). At this point you can close the Winzip program or 
go to File and choose Open Archive to open another file to unzip. 

Now that it is extracted - for the sake of this discussion let's assume it's 
a program to install - go to the directory you extracted it to and run the 
setup file. After this is done you can usually delete the files. Either 
way, the original .zip file remains intact until you physically delete it. 
You can tuck it away somewhere in case you ever want to extract it again. 

Winzip (and other Zip programs) will also extract other compressed file types 
such as cabinet files (.cab) that Microsoft uses for setup files. Need to 
extract an original copy of a .DLL from the Windows Setup Cabinet Files? 
Simply double click the cabinet file containing the desired file and it 
will open with WinZip. Highlight the file you want to extract, and click 
the extract button. With a file highlighted, the default choice is 
"selected files". Choose a directory to extract it to, and click the 
extract button in the dialogue. 

Unzipping files is pretty straight forward and easy. Creating ZIP files is 
also easy, and we'll cover that in the next section. 

Zipping Files

There are a few ways to do this. You can go to Windows Explorer and 
highlight a single file and then right click and choose Add to 
(filename).zip from the menu. That will create a .zip file with the 
filename of the selected file. You can also choose Add to Zip in which case 
it will open WinZip at the Add to Archive dialogue and you can choose a 
filename and options. If you highlight multiple files Add to Zip is the 
only option available (but it's what you want anyway). If you are using 
another Zip tool, the right-click options may be labeled slightly different, 
but they are the same as the WinZip right-click options.

The other way to do this (this is how I would do it) is to open the WinZip 
program and click the "New" button or from the File menu choose New Archive. 
You are then presented with a dialogue to browse for the destination and 
give it a filename (with the .zip extension). Do that, then click Open and 
another dialogue will pop up where you browse for and select the files you want 
to add to the archive. To select multiple files hold the Ctrl key as you click 
on them. Choose the option for Maximum Compression (might as well). Also, 
if you are including folders in the zip file make sure you select the 
option to "Include Subfolders". If you want to preserve the entire folder 
structure including the folder that the files are in, check the box "save 
extra folder info". This means, the person unzipping the file will get the 
folder structure intact when they unzip it. (unless they uncheck the box in 
the unzip dialogue "use folder names"). When you are finished, you will 
have a .zip file in the directory you created it. You should test it, 
simply double-click it and if it opens, it's ok. If you really want to 
check it you can invoke the CRC check by choosing Test from the Action 
menu. 

Create Self-Extracting Executable Files

What if the person you are sending the file to doesn't have a ZIP utility? 
Then you can create a self-extracting executable file, in other words a 
program that will automatically extract the files when double-clicked or 
run. In order to do this, you have to first create a .zip file. After you 
have created it, you can immediately choose "Make EXE File" from the Action 
Menu. When you do this, a dialogue pops up where you can choose the default 
extract to location (e.g. %temp% which would be their default temp 
directory or choose a directory name. The directory will get created for 
them if they go with the default options when they run it). They will have 
the option of choosing an alternate location so don't worry. Alternatively, 
if you right click on a .zip file in Windows Explorer you'll see an option 
to create a self extracting exe file. Either way, once the file is created 
you should test it by double clicking it. 



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